THE ISLE OF PORTLAND. 
339 
tranquilly subsided (like many subterranean forests 
of the modern epoch*) beneath a body of fresh 
water, sufHciently profound to admit of the accu- 
mulation of the limestone and fluviatile strata that 
compose the Wealden. What contemporaneous 
changes took place in other parts of Europe, it 
would be foreign to our jiurpose, and perhaps, in 
the present state of our knowledge, in vain to en- 
quire ; but we may remark, tliat the submergence 
of so extensive a tract of country, jirobably j)ro- 
duced in other regions important mutations in 
the relative level of the land and water, t At this 
epoch, then, the land and its tropical forest sank 
to the deptli of many hundred feet, and became 
the bed of a vast lake or estuary, into whicli we 
have the clearest evidence that a river flowed, and 
formed a delta, made up of the debris of the rocks 
which composed its bed, intermixed with the re- 
mains of the animals and vegetables of the country 
from whence its waters were derived ; for, as Mr. 
Bakewell has sagaciously remarked!, a river that 
* Vide p. 18. 
f M. Elie de Beaumont has shown, that the higher ridges in eastern 
France, of the Cote d’Or, and iNIount Pilas, and a portion of the Jura 
chain, were all elevated after the formation of the Oolite was completed, 
and before the deposition of the chalk ; these elevatory movements 
therefore took place at the Iguanodon period, and may have been con- 
nected with the physical mutations of the south-east of England men- 
tioned in the text. The immense area over which the effects of an 
earthquake may extend, was remarkably exemplified in that of Lisbon, 
in 1755. It was most violent in Portugal, Spain, and the north of 
Africa; but the whole of Europe, and even the West Indies, felt the 
shock on the same day. Consult Mr. LyelVs “ Principles of Geology," 
vol. i. p. -I39. 
In his correspondence with the Author. 
Z *2 
